I was in Chicago the night of the seventh game of the 2016 World Series. As a Canadian, I’m more of a hockey guy—but I couldn’t help get swept up by the excitement that night.

The Chicago Cubs used to be Major League Baseball’s punch line for any joke about perpetual losers—until Theo Epstein. Epstein, known for helping break the “Curse of the Bambino” with the Boston Red Sox at the tender age of 31, also led the Cubs to their first World Series win in 2016 after a 108-year hiatus. Clearly, Epstein knows how to win.

His extraordinary feat was lauded in Fortune, where he made the top spot on the World’s Greatest Leaders list, but what makes him truly remarkable is what he learned from his years with the Red Sox. In his book, The Cubs Way, author and Sports Illustrated senior baseball writer Tom Verducci, describes it this way:

“Once he’d joined the Cubs, Epstein gave his scouts very specific marching orders. On every prospect he wanted the area scout to give three examples of how that player responded to adversity on the field and three examples of how that player responded to adversity off the field.”

In other words, Epstein realized the importance of character and wanted to build a psychologically healthy workplace. His previous approach with the Red Sox, which was similar to the obsession with statistics, number-crunching and little-known niche talents similar to the movie Moneyball, wasn’t sustainable. By the end of his tenure the team was falling apart. He realized that no amount of data could account for character and chemistry.